Patent EP-3232207-A1 (EP)
Inventor: LEON MARTINEZ VICENTE
IPC: G01R21/06
Filed: 2015-12-04
Abstract: The invention relates to a method and a system for measuring imbalances in an electrical grid. The method comprises the steps of obtaining effective values and arguments of the phase voltages and currents at the fundamental frequency; calculating the effective value and the argument of the positive sequence voltages and the effective values of the negative sequence voltages; determining the active and reactive powers of each of the phases at the fundamental frequency; and calculating the value of the imbalance power vector according to the following equation:              S     ‾         u     =     V     +           2   +   2     δ   u   2     +   2     δ   A   2         ⋅       |           P     A   1             V     A   1           cos       α     +       −     α     A   1         +   j             Q     ‾           A   1             V     A   1           sin       α     +       −     α   1       +     a   2           P     B   1             V     B   1           cos       α     +       −     α     B   1         +   +     ja   2               Q     ‾           B   1             V     B   1           sin       α     +       −     α     B   1         +   a           P     C   1             V     C   1           cos       α     +       −     α     C   1         +   ja             Q     ‾           C   1             V     C   1           sin       α     +       −     α     C   1         |   ⋅     p     ‾           +   +     V     +           2   +   2     δ   u   2     +   2     δ   A   2         ⋅         j         P     A   1             V     A   1           sin       α     +       −     α     A   1         +             Q     ‾           A   1             V     A   1           cos       α     +       −     α     A   1         +   j     a   2           P     B   1             V     B   1           sin       α     +       −     α     B   1         +   +     a   2               Q     ‾           B   1             V     B   1           cos       α     +       −     α     B   1         +   ja           P     C   1             V     C   1           sin       α     +       −     α     C   1         +   a             Q     ‾           C   1             V     C   1           cos       α     +       −     α     C   1         +     ⋅     q     ‾         +   +     V     +             δ   u   2     +     δ   A   2         ⋅                 ∑       x   =   A   ,   B   ,   C                   P     x   1             V     x   1           cos       α     +       −     α     x   1         +   j             Q     ‾           x   1             V     x   1           sin       α     +       −     α     x   1         +   j         P     x   1             V     x   1           sin       α     +       −     α     x   1         +             Q     ‾           x   1             V     x   1           cos       α     +       −     α     x   1                 ⋅     z     ‾              wherein  a =1∠120°; j is the imaginary unit; δ U  = V - /V +  and δ A  = V 0 /V +  are the degrees of imbalance and asymmetry, respectively, of the phase voltages; and  p ,  q ,  z  are the orthogonal unit vectors defining the space itself of the imbalance power vector.